Despite the recent push to improve our diet and get us exercising (thanks, Michelle Obama), national obesity rates haven’t budged much over the past few years, the latest government statistics show.

In 2010, about 35.7% of U.S. adults — nearly 78 million people — were obese. That’s up from 30.5% in 2000, but not much of a difference from 33.7% in 2008.

Does that mean our attempts at healthy living — giving up the French fries and sodas, and logging endless miles on the treadmill — have been for nothing? Not quite. Public health experts say that it may be too soon to see an actual decline in obesity rates, since the nation’s efforts to slim down began relatively recently. And while it would be encouraging to see obesity rates in the U.S. start to dip, experts say the current data are still inspiring — at least the U.S. isn’t getting fatter overall.

The latest report, published Tuesday in the Journal of the American Medical Association, is based on data from the National Center for Health Statistics (NCHS), which surveys a representative sample of the U.S. population on a number of health measures, including height and weight. Body mass index (BMI), which is used to determine obesity (a BMI of over 30 is considered obese), is then calculated from these readings. The statistics are collected and released every two years.

The researchers, led by Katherine Flegal and Cynthia Ogden at the NCHS at the Centers for Disease Control and Prevention (CDC), found that between 1960 and 1980, U.S. obesity rates remained relatively stable. Between the 1976-80 and 1988-94 surveys, obesity increased by 8%, then rose again between that time and 1999-2000. Between 1999 and 2008, the rates started to level off.

That plateau continued in the most recent survey, which included data from 2009-10. But the flattening of the curve hides some interesting trends that are worth noting and may help identify segments of the population that are struggling most with weight. In the 1999-2000 survey, more women than men were obese, but by 2009-10, the rate of obesity was almost identical among the sexes. In 2010, 35.5% of men were obese, up from 27.5% in 2000. About 35.7% of women were also obese in 2010, roughly the same rate as in 2000. “Men have caught up to women with respect to their prevalence of obesity,” says Ogden. “We continue to see an inching up of obesity among males.”

The same shift was true among teens: obesity in teen boys increased between 1999-2000 and 2009-10, while the rate among girls remained about the same. That trend largely fueled the overall increase in obesity in children and adolescents aged 2 to 19, from 13.9% in 2000 to 16.9%, or nearly 13 million, today. Overall, however, like in adults, the teen obesity rate has showed a leveling off over the past few years; the current rate has been holding steady since 2007-08.

The fact that the obesity rates aren’t declining doesn’t mean that public health programs promoting healthier diets and more physical activity aren’t working, or that our individual efforts to shed pounds are in vain. Dr. William Dietz, director of the division of nutrition, physical activity and obesity at the CDC, says the latest statistics do represent progress. He compares anti-obesity efforts to those designed to reduce smoking, which began in the 1950s with the first reports that smoking could cause cancer. Cigarette use remained flat for the first 10 to 15 years, before finally starting to decline in the 1980s, when policy-based initiatives, such as cigarette taxes and smoking bans in public areas, were put in place.

“I believe we’re not yet at the place with obesity where tobacco was when cigarette use started to drop,” says Dietz. “Nutrition programs and physical activity efforts have only just begun to kick in, and haven’t had much time to operate. It takes time before the effects of policy change begin to show benefit in terms of behavior changes.”

Dietz believes it’s too early to expect the obesity epidemic to start reversing itself, but is confident that continued efforts not only to educate, but also to make it easier for Americans to eat healthy and exercise more will ultimately lead to a downturn in the obesity curve. That’s especially true for subgroups of Americans, including men and teen boys as well as African-American and Mexican-American women, who showed increases in obesity over the past 12 years.